Case Study

Effective flight testing of U.S. military aircraft and the subsystems they depend on is a complex and ongoing challenge, and it's important that every Air Force test facility use standardized approaches to in-flight testing.

Achieving and maintaining such flight-test standardization is the job of the Range Commanders Council (RCC), a group that oversees how testing is done on U.S. test ranges. Among the RCC's most important protocols are the Inter-Range Instrumentation Group (IRIG) standards, a broad group of procedures that includes the "IRIG 106 Chapter 10" standard, which covers digital flight-data recorders.

A digital flight data recorder consists principally of a hard drive that records a wide variety of information during flight testing. This data includes numerous functions such as instrument readings, along with video taken of instrument panels, cockpit displays or views outside the aircraft.

"Chapter 10 is an important and complex standard, really a de facto standard for how the Department of Defense does digital flight-data recording on test ranges," said Robert W. Baggerman, a research engineer at the Georgia Tech Research Institute (GTRI). "It describes how a digital flight-data recorder will work, what the resulting data will look like, and how you interface to it and interpret it."

To help support the Air Force's flight-test efforts, Baggerman has developed a handbook to aid those who deal with flight-test data. Known as the "IRIG 106-07 Chapter 10 Programming Handbook" - the Programmers Handbook for short - the 183-page document is now available in PDF format to the U.S. flight testing community and to others concerned with flight testing.

The work was funded by the Air Force. It was facilitated by the Military Sensing Information Analysis Center (SENSIAC), a Department of Defense information analysis center operated by Georgia Tech under contract to the Defense Technical Information Center.

"The handbook basically functions as a guide to the Chapter 10 standard," said Baggerman, who is a member of the Recorders and Reproducers Committee of the RCC's Telemetry Group. "It explains some areas of the standard that might need additional interpretation. It also provides applications useful for data analysis, as well as a considerable number of source-code examples to aid programmers."

Previously, Baggerman explained, U.S. aircraft relayed in-flight test information down to ground stations via wireless radio telemetry links. Telemetry is still used today, but increased data-bandwidth requirements and the advent of miniaturized rugged storage have resulted in the development of on-board flight-data recording. After a test flight, the flight-data recorder's hard drive is plugged into a computer, and its information is analyzed to ensure that the systems under test are working correctly.

One significant feature of the Programmers Handbook, Baggerman said, is that the included applications and code examples are open source. That means all software source code is included and can be modified by users to suit their needs.

"We have written an open-source library, which includes a library for reading and writing data," he said. "Also available in an open-source format are applications for doing such manipulations as data extraction and filtering."Baggerman added that the open-source approach is becoming more attractive to the military for a number of applications. For one thing, open-source code can often be changed in-house, which generally results in speedier software upgrades than proprietary software can offer.

The IRIG 106-07 Chapter 10 Programming Handbook has already been downloaded several hundred times, Baggerman said. The publication is publicly available in PDF format.

"GTRI is always looking for ways to enhance U.S. testing efforts," Baggerman said. "Whenever we can leverage our flight-test experience to support the testing community, then that's what we like to do."